Fixes incorrect parsing of window specification Teiid SQL

*.jjt
 * If teiid version is less than 8.6 then a parsing exception should be
   thrown if agg is not an aggregate symbol
 * Name should be set on the newly create aggregate symbol

* Aggregate8Symbol
 * valueOf will throw an IAE which is incorrect. The aggregate function
   should be assigned USER_DEFINED instead

* TestQuery86Parser
 * Overrides failing version in preceding teiid version tests since the
   functionality was 'enhanced' in teiid 8.6
Improves error handling of Teiid Parser in sequencer

* Rather than an exception/error being immediately thrown, the parser
  logs it and attempts to continue in order to be more comprehensive.

* QueryParser still throws an exception if TeiidParser delegate contains
  errors but will return an exception message containing all the error
  messages accrued.

* TeiidParser error messages improved to try and give more clarity when
  certain mistakes have been made.

* Includes fix applied to teiid client parser concerning aggregates and
  functions from previous commit.